The name "salt rising bread" is said to arise from use of salt as a
warming environemnt for the bread starter. As an instance see the
rec.food.baking posting "Re Q's about Salt Rising Bread; 07 Nov 1997
by Johnson". Johnson and Fannie Farmer, like most if not all others,
does not cite a credible historical reference for this idea.
Please find a primary historical account for the notion that salt
rising bread is so-named because warm salt was used in creating the
starter. Johnson would not pass himself off as a primary source and
the Fannie Farmer citation is equally bogus.
(Make that "I will wait up to one month." rather than "I want to wait
one month.")

I found a comment that the reason for using salt was to inhibit the
growth of any natural yeasts that might have contaminated the starter,
thus encouraging the bacteria which give the bread its characteristic
taste and smell: http://www.geocities.com/napavalley/6454/breads.html
There's something about the science behind it at
http://web.mountain.net/~petsonk/
I've also found a biography of Ann Willden Johnson (OUR PIONEER MOTHER
As told to LENORA JOHNSON MACDONALD 1912-1920,
http://handfamily.org/prefpion.htm) Chapter 2, at
http://handfamily.org/chp2pion.htm has the following extract referring
to the early 1860s: "After a time our provisions gave out. Soon we
found the "cached" wheat, or we might have starved. The wheat was all
we had to live on. At first we ate it boiled, and then my husband
decided to make a Danish mill of two flat stones. We ground the wheat
and sifted it through my veil, then I made some "salt rising" bread;
though it was somewhat gritty, - we did not care as it was far better
than the boiled wheat."

Paul:
Jenny Bardwell and Susan Ray Brown are well known to me; we have
corresponded extensively about salt rising bread. They admit that
they have no idea about the origin of the supposed naming convention.
I have run the same Google queries you used with the results you
obtained. A report of my rather extensive experimentation with salt
rising bread is in the throes of publication. I have pretty well
demonstrated that salt is a necessary part of an SRB starter. I
characterize the warming salt idea as a latter day theory because
despite many attempts to find the origin, no person or reference has
ever referred to an historical reference. I would quickly modify my
account if there is credible evidence for the naming notion.
I have also sought references to use and storage of household salt in
the 18th and 19th centuries.. Thus far, I have found nothing general.
In particular, I have found no account that describes a practice of
holding salt near a fireplace to keep it dry.

Tehuti:
You followed a trail that I thought might lead to something; i.e.,
biographical accounts and diaries from the 18th and 19th centuries.
The term seems to appear often enough, but always in contexts where it
was assumed well-known. There are a couple of 19th century newspaper
references about prizes awarded for SRB in baking competitions.
I tried to learn something from Mormon Church records, but, apart from
geneology data, there doesn't seem to be much available on the Web.

Paul:
Seems like we both misfired. The Google Answers blurb declares that
Google and other sources are available to individuals such as yourself
and, because I knew Google to be a dry hole, I assumed that the
sources, unavailable to me, would have an answer. You assumed that
hearsay accumulated from Google would be satisfactory. As the saying
has it to "assume" makes an ass of "u" "me".
Perhaps I should have warned you that my Google inquiries had been
extensive and unproductive. As you comment, it won't happen again!
Sorensson

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